CVE-2015-2715 in Firefox
Summary
by MITRE
Race condition in the nsThreadManager::RegisterCurrentThread function in Mozilla Firefox before 38.0 allows remote attackers to execute arbitrary code or cause a denial of service (use-after-free and heap memory corruption) by leveraging improper Media Decoder Thread creation at the time of a shutdown.
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Analysis
by VulDB Data Team • 05/17/2022
The vulnerability identified as CVE-2015-2715 represents a critical race condition within Mozilla Firefox's threading implementation that enables remote code execution and denial of service attacks. This flaw exists in the nsThreadManager::RegisterCurrentThread function and affects Firefox versions prior to 38.0, making it a significant security concern for users of older browser versions. The vulnerability stems from improper handling of Media Decoder Thread creation during shutdown sequences, creating a window where malicious actors can exploit the timing gap between thread registration and cleanup operations. The race condition occurs when the browser attempts to register a thread while simultaneously shutting down the media decoding subsystem, leading to unpredictable memory states that attackers can manipulate for malicious purposes.
The technical nature of this vulnerability manifests as a use-after-free condition combined with heap memory corruption, both of which fall under the CWE-362 category of race conditions and CWE-416 for use-after-free errors. When Firefox processes media content and encounters a shutdown scenario, the thread management system fails to properly synchronize the registration and destruction of Media Decoder Threads, creating a scenario where freed memory locations can be accessed and overwritten by subsequent operations. This improper synchronization allows attackers to craft malicious web content that triggers the vulnerable code path, potentially leading to arbitrary code execution within the browser's memory space. The heap corruption aspect of the vulnerability can result in memory layout changes that make exploitation more reliable and can also cause the browser to crash, resulting in denial of service conditions.
The operational impact of CVE-2015-2715 extends beyond simple exploitation as it represents a fundamental flaw in Firefox's threading architecture that can be leveraged across various attack vectors. Attackers can deliver malicious content through web pages that, when loaded, trigger the race condition during media processing shutdown, potentially allowing them to execute arbitrary code with the privileges of the browser process. This vulnerability is particularly dangerous because it can be exploited through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website. The attack surface includes any web content that utilizes media decoding functionality, making it a widespread concern that affects millions of users who rely on Firefox for daily browsing activities. The vulnerability's exploitation can lead to complete system compromise when combined with other attack techniques, as successful exploitation allows attackers to bypass security restrictions and potentially gain access to sensitive user data.
Mitigation strategies for CVE-2015-2715 primarily focus on immediate browser updates to versions 38.0 or later, where the race condition has been resolved through improved thread synchronization mechanisms. Users should also implement additional security measures including browser hardening techniques, regular security updates, and monitoring for suspicious web content. Security researchers and organizations should monitor for exploitation attempts and consider implementing web content filtering solutions that can detect and block known malicious patterns associated with this vulnerability. The fix implemented by Mozilla addressed the underlying race condition by ensuring proper synchronization between thread registration and shutdown operations, preventing the use-after-free scenario that made exploitation possible. Organizations should also consider implementing security awareness training to help users recognize potentially malicious web content and avoid visiting compromised websites that might exploit this vulnerability. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreter and T1203 for Exploitation for Client Execution, highlighting the need for comprehensive security measures that address both the technical vulnerability and potential exploitation techniques.